Method and system for maintaining an engine coolant level

ABSTRACT

Methods and systems are provided for maintaining a desired engine coolant level and a relative glycol amount in the engine coolant by using water sourced from on-board vehicle systems. In one example, a method may include supplying water to the engine coolant reservoir in response to the engine coolant level decreasing below a threshold. Also, a relative glycol amount in the coolant may be maintained at a threshold amount by adding water to the coolant in response to a relative glycol increasing above the threshold.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. patent applicationSer. No. 15/431,187, entitled “METHOD AND SYSTEM FOR MAINTAINING ANENGINE COOLANT LEVEL,” filed on Feb. 13, 2017. The entire contents ofthe above-referenced application are hereby incorporated by reference inits entirety for all purposes.

FIELD

The present description relates generally to methods and systems formaintaining a desired coolant level and a relative glycol amount in anengine coolant, for example by using water recovered from one or morevehicle systems.

BACKGROUND/SUMMARY

In automotive thermal management, coolant level in a cooling system isclosely controlled for improved engine efficiency and emissions quality.The coolant may comprise a mixture of water and glycol and a chemicalbalance between the two components is maintained to improve theperformance of the cooling system. As the coolant is circulated throughengine components to control engine temperature, over time, due toevaporation, the water content of the coolant may reduce and also theremay be an overall reduction in the coolant level and an increase in thecoolant glycol level. Also, leakages may cause a decrease in the coolantglycol level.

Various approaches are provided for maintaining the water balance in anengine coolant system. In one example, as shown in U.S. Pat. No.6,171,718, Murach et al. discloses a method of monitoring coolant levelin a coolant reservoir inside a fuel cell used in a vehicle. If thecoolant level reduces to below a threshold, the exhaust stream may berouted through a supercharger, wherein the exhaust stream ispressurized. The pressurized exhaust stream is then passed through apressurized condensing heat exchanger and water is recovered from thepressurized exhaust stream. This recovered water may be used to restorethe water level in the coolant.

However, the inventors herein have recognized potential disadvantageswith the above approach. As one example, in the approach shown by Murachet al., operating parameters of the fuel cell may have to be adjusted inorder to produce condensed water to be added to the coolant system. Thechange in the operating parameters may adversely affect the operation ofthe fuel cell and the associated vehicle. Also, in the aforementionedapproach, the glycol level in the coolant is not taken into accountwhile adjusting the coolant level. Due to higher coolant temperatures, asignificant amount of water in the coolant may evaporate and a higherrelative amount of glycol in the coolant may cause over-heating of thecoolant thereby adversely affecting performance of the cooling systemand the overall engine performance. Further, use of water stored in areservoir (for coolant system maintenance) which needs to be externallyrefilled and maintained may add to the maintenance cost of the vehicle.

In one example, the issues described above may be addressed by an enginemethod comprising: in response to a relative amount of glycol in anengine coolant being higher than a threshold amount, and/or in responseto an engine coolant level being lower than a threshold coolant level,supplying water from an on-board water collection system to a coolantreservoir; and in response to the relative amount of glycol in theengine coolant being lower than the threshold amount, setting adiagnostic code. In this way, by monitoring the coolant level and glycollevel in a coolant and by opportunistically adding water harvested fromone or more vehicle components to the coolant, water glycol balance andthe coolant level may be maintained in the coolant system.

As one example, the coolant level in a coolant reservoir may be measuredvia a float sensor or may be estimated based on a coolant temperaturesensor output data. The glycol level in the coolant may be directlymeasured via a glycol level sensor or estimated from the coolant levelin the reservoir. If it is inferred that the relative amount of glycolin the coolant is higher than a threshold and/or if the coolant level inthe reservoir is lower than a threshold, an amount of water may be addedto the coolant such that the coolant level increases to the thresholdlevel, and the relative glycol amount decreases to the threshold amount.The amount of water to be added may be based on the one or more of adifference between the current coolant level and the threshold and thedifference between the actual relative glycol amount and the desiredrelative glycol amount. The water to be added to the coolant system maybe harvested from condensate accumulated in a plurality of vehiclecomponents. As such, a significant amount of water condenses at anevaporator of an air conditioning system and this water may be stored ina reservoir to be opportunistically used to maintain the coolant level.In addition, water may be recovered from vehicle door seal channels,exhaust system, intake system charge air cooler, fuel system, etc. Eachof the on-board water recovery systems may have individual reservoirs tocollect the water which may then be routed to a centralized water tankvia a plurality of pumps and from thereon the water may be supplied tothe coolant reservoir based on demand. In addition, the water reservoirsmay be coupled to drainage lines to remove any excess water. Beforeadding the water to the coolant reservoir, the purity of water may alsobe determined and in response to a lower than threshold water quality,water stored in the tank may be drained. If it is determined that therelative glycol amount in the coolant is lower than the thresholdamount, a diagnostic code may be set notifying an operator to externallysupply glycol.

In this way, by sourcing water from a plurality of existing vehiclecomponents such as the air conditioning system for use in the coolantsystem, engine operating conditions may not have to be altered for waterrecovery. Also, by internally sourcing the water, dependence on externalwater supply may be reduced which may also reduce the maintenance costof externally supplying water to the coolant system. By sourcing waterfrom a plurality of vehicle systems, burden on any one particular systemmay be reduced. The technical effect of estimating the glycol level andadjusting the water level in the coolant order to maintain a desiredwater glycol balance is that overheating and degradation of the coolantsystem may be reduced. Also, by assessing the water quality beforeadding the water to the coolant system, possibility of contamination ofthe coolant system caused due to excessive glycol content in coolant maybe reduced. Overall, by maintaining the chemical balance in the coolantsystem, engine operation may be improved.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic diagram of an engine system including anon-board water recovery system.

FIG. 2 shows a flow chart illustrating an example method that may beimplemented for maintaining a coolant level and a relative glycol amountin the coolant system.

FIG. 3 shows an example maintenance of a coolant level and a relativeglycol amount in the coolant system, according to the presentdisclosure.

DETAILED DESCRIPTION

The following description relates to systems and methods for maintaininga coolant level and a water glycol balance in an engine coolant by usingwater recovered from one or more vehicle systems. An example embodimentof an engine system with a coolant system and an on-board water recoverysystem is shown in FIG. 1. A controller may be configured to perform acontrol routine, such as the example routine of FIG. 2, to maintain adesired coolant level and a water glycol balance in the engine coolantsystem. An example of maintenance of the coolant level and the waterglycol chemical balance in the coolant system is shown in FIG. 3.

FIG. 1 shows an example embodiment of an engine system 100 configuredwith an on-board water recovery system 60. Engine system 100 is coupledin motor vehicle 102, illustrated schematically. Engine system 100includes an engine 10, depicted herein as a boosted engine coupled to aturbocharger 13 including a compressor 14 driven by a turbine 116.Specifically, fresh air is introduced along intake passage 142 intoengine 10 via air cleaner 31 and flows to compressor 14. The compressormay be a suitable intake-air compressor, such as a motor-driven ordriveshaft driven supercharger compressor. In the engine system 100, thecompressor is shown as a turbocharger compressor mechanically coupled toturbine 116 via a shaft 19, the turbine 116 driven by expanding engineexhaust. In one embodiment, the compressor and turbine may be coupledwithin a twin scroll turbocharger. In another embodiment, theturbocharger may be a variable geometry turbocharger (VGT), whereturbine geometry is actively varied as a function of engine speed andother operating conditions.

As shown in FIG. 1, compressor 14 is coupled, through charge air cooler(CAC) 118 to throttle valve (e.g., intake throttle) 20. The CAC 118 maybe an air-to-air or air-to-coolant heat exchanger, for example. Throttlevalve 20 is coupled to engine intake manifold 122. From the compressor14, the hot compressed air charge enters the inlet of the CAC 118, coolsas it travels through the CAC, and then exits to pass through thethrottle valve 20 to the intake manifold 122. In the embodiment shown inFIG. 1, the pressure of the air charge within the intake manifold issensed by manifold absolute pressure (MAP) sensor 124 and a boostpressure is sensed by boost pressure sensor 24. A compressor by-passvalve (not shown) may be coupled in series between the inlet and theoutlet of compressor 14. The compressor by-pass valve may be a normallyclosed valve configured to open under selected operating conditions torelieve excess boost pressure. For example, the compressor by-pass valvemay be opened responsive to compressor surge.

Intake manifold 122 is coupled to a series of combustion chambers orcylinders 180 through a series of intake valves (not shown) and intakerunners (e.g., intake ports) 185. As shown in FIG. 1, the intakemanifold 122 is arranged upstream of all combustion chambers 180 ofengine 10. Additional sensors, such as manifold charge temperature (MCT)sensor 23 and air charge temperature sensor (ACT) 25 may be included todetermine the temperature of intake air at the respective locations inthe intake passage. The air temperature may be further used inconjunction with an engine coolant temperature to compute the amount offuel that is delivered to the engine, for example. Each combustionchamber may further include a knock sensor 183 for identifying anddifferentiating abnormal combustion events, such as knock andpre-ignition. In alternate embodiments, one or more knock sensors 183may be coupled to selected locations of the engine block.

The combustion chambers are further coupled to exhaust manifold 136 viaa series of exhaust valves (not shown). The combustion chambers 180 arecapped by cylinder head 182 and coupled to fuel injectors 179 (whileonly one fuel injector is shown in FIG. 1, each combustion chamberincludes a fuel injector coupled thereto). Fuel may be delivered to fuelinjector 179 by a fuel system (not shown) including a fuel tank, a fuelpump, and a fuel rail. Fuel injector 179 may be configured as a directinjector for injecting fuel directly into combustion chamber 180, or asa port injector for injecting fuel into an intake port upstream of anintake valve of the combustion chamber 180.

In the depicted embodiment, a single exhaust manifold 136 is shown.However, in other embodiments, the exhaust manifold may include aplurality of exhaust manifold sections. Configurations having aplurality of exhaust manifold sections may enable effluent fromdifferent combustion chambers to be directed to different locations inthe engine system. Universal Exhaust Gas Oxygen (UEGO) sensor 126 isshown coupled to exhaust manifold 136 upstream of turbine 116.Alternatively, a two-state exhaust gas oxygen sensor may be substitutedfor UEGO sensor 126.

As shown in FIG. 1, exhaust from the one or more exhaust manifoldsections is directed to turbine 116 to drive the turbine. When reducedturbine torque is desired, some exhaust may be directed instead througha waste gate (not shown), by-passing the turbine. The combined flow fromthe turbine and the waste gate then flows through emission controldevice 170. In general, one or more emission control devices 170 mayinclude one or more exhaust after-treatment catalysts configured tocatalytically treat the exhaust flow, and thereby reduce an amount ofone or more substances in the exhaust flow.

All or part of the treated exhaust from emission control device 170 maybe released into the atmosphere via exhaust conduit 35. Depending onoperating conditions, however, some exhaust may be diverted instead toan exhaust gas recirculation (EGR) passage 151, through EGR cooler 50and EGR valve 152, to the inlet of compressor 14. In this manner, thecompressor is configured to admit exhaust tapped from downstream ofturbine 116. The EGR valve 152 may be opened to admit a controlledamount of cooled exhaust gas to the compressor inlet for desirablecombustion and emissions-control performance. In this way, engine system100 is adapted to provide external, low-pressure (LP) EGR. The rotationof the compressor, in addition to the relatively long LP EGR flow pathin engine system 100, provides excellent homogenization of the exhaustgas into the intake air charge. Further, the disposition of EGR take-offand mixing points provides effective cooling of the exhaust gas forincreased available EGR mass and increased performance. In otherembodiments, the EGR system may be a high pressure EGR system with EGRpassage 151 connecting from upstream of the turbine 116 to downstream ofthe compressor 14. In some embodiments, the MCT sensor 23 may bepositioned to determine the manifold charge temperature, and may includeair and exhaust recirculated through the EGR passage 151.

The on-board water recovery system 60 may include a water storage tank63, a water lift pump 162, a collection system 72, and a water fillingpassage 69. Water stored in water tank 63 is delivered to a reservoir 15of an engine coolant system via conduits or lines 161. A flow regulatorvalve 163 may regulate flow of water from the water storage tank 63 tothe coolant reservoir 15. The coolant reservoir 15 may include a floatsensor 16 and a glycol level sensor 17 to estimate a level of coolant inthe coolant reservoir and a relative amount of glycol in the coolant,respectively. Coolant from the coolant reservoir 15 may be circulatedthrough the engine via the coolant line 171. An engine coolanttemperature sensor 127 may be coupled to the coolant line 171 toestimate coolant temperature and engine temperature.

Water storage tank 63 may include a water level sensor 65 and a watertemperature sensor 67, which may relay information regarding waterconditions to controller 12. For example, in freezing conditions, watertemperature sensor 67 detects whether the water in tank 63 is frozen oravailable for injection. In some embodiments, an engine coolant passage(not shown) may be thermally coupled with storage tank 63 to thaw frozenwater. The level of water stored in water tank 63, as identified bywater level sensor 65, may be communicated to the vehicle operator. Forexample, a water gauge or indication on a vehicle instrument panel (notshown) may be used to communicate the level of water. If the level ofwater in the water tank 63 is higher than a threshold level, it may beinferred that there is sufficient water available for supply to thecoolant reservoir 15, and accordingly water supply may be enabled by thecontroller, as needed. Else, if the level of water in the water tank 63is lower than the threshold level, it may be inferred that there isinsufficient water available for injection, and therefore water supplymay be disabled by the controller until the tank 63 is refilled. Waterfrom the on-board water collection system 60 may also be used for waterinjection to the engine.

In the depicted embodiment, water storage tank 63 may be automaticallyrefilled by the collection system 72 via water tank filling passage 76.Also, the water storage tank 63 may be manually refilled via waterfilling passage 69. Collection system 72 may be coupled to one or morevehicle components 74 so that the water storage tank can be refilledon-board the vehicle with condensate collected from various engine orvehicle systems. In one example, collection system 72 may be coupledwith an EGR system and/or exhaust system to collect water condensed fromexhaust passing through the system. In another example, collectionsystem 72 may be coupled with an air conditioning system (not shown) forcollected water condensed from air passing through an evaporator. In yetanother example, collection system 72 may be coupled with an externalvehicle surface (such as door seal channels in the door) to collect rainor atmospheric condensation. A funnel may be positioned under a cupholder in the vehicle cabin to allow recovery of water spills occurringin a container positioned at the cup holder. Further, water may becollected from the charge air cooler 118 and other colder parts of theintake system where water condensation may take place. Water may becollected from an on-board fuel cell and components of the exhaustsystem such as from an exhaust heat exchanger. Also, water may berecovered from fuel. As an example, as fuel is routed to the fuel tank,a mass centrifugal water separator may be used to remove water from thefuel and this water may be routed to the water storage tank 63. Manualfiling of water may be possible via a manual filling passage 69fluidically coupled to a filter 68, which may remove some impuritiescontained in the water.

Each of the vehicle components 74 from which water may be recovered mayinclude a reservoir or a tray for collecting the water. Each reservoiror tray of the vehicle components 74 may be coupled to the water storagetank 63 via water recovery lines which may further comprise individualpumps. In one example, each reservoir or tray of the vehicle components74 may be positioned at a higher elevation relative to the water storagetank 63 to allow water to flow to the water storage tank 63 by the forceof gravity without the requirement of additional pumps. There may be oneor more filters in the water recovery system 60 to remove impuritiesfrom the water entering the water storage tank 63. Water level sensorsand pressure sensors may be coupled to each of the reservoirs or trays.Clogging in filters and/or leakages in the reservoirs may be detectedbased on inputs from the pressure sensor. As an example, an unexpectedincrease in water pressure may be observed in one or more reservoirswhen the filter corresponding to the reservoir is clogged. A reverseflow pump may be included in the water line coupling each of thereservoirs to the water storage tank 63. The reverse flow pump may beoperated to reverse the direction of water flow through the water lineto clean the filter and purge the line. Once the water lines have beencleaned and purged, the water from the tank 63 may be drained andrefilling of water may be initiated.

A drain 92 including a drain valve 91 may be used to drain water fromthe water storage tank 63 to a location outside the vehicle (e.g., ontothe road), such as when a quality of the water is deemed to be lowerthan a threshold and not suitable for supply to the coolant reservoir(e.g., due to high conductivity, high particulate matter content). Inorder to reduce the possibility of water freezing in the tank 63, watermay be drained from the tank 63 during conditions when water temperaturein the tank 63 is predicted to be below freezing point. If the vehicleengine is shut-down for a prolonged period of time during cold ambientconditions, the water from the tank 63 may be drained to reduce thepossibility of freezing. In one example, engine coolant may becirculated around the water tank 63 or the water tank 63 may beinsulated using a phase change material in order to reduce freezing ofthe water in the tank 63. During cold conditions, the phase changematerial may supply heat to the water tank 63 to maintain watertemperature above the freezing point. Also, for electric hybridvehicles, during colder ambient conditions, the water tank 63 may beexternally heated by passing electric current through the walls of thetank 63 when the vehicle is plugged in.

As such, the quality of the water may be assessed based on the output ofconductivity sensor 93 coupled to the on-board water collection system60, in water line 161. In other examples, sensor 93 may be a capacitancesensor, optical sensor, turbidity sensor, density sensor, or some othertype of water quality sensor. In this way, if a water level in the watertank 63 is higher than a first threshold or if a predicted watertemperature is lower than a freezing temperature, at least a portion ofwater from the water tank may be drained, and if the water level in thewater tank is lower than a second threshold, the water tank may berefilled with water collected from the one or more vehicle systems, thefirst threshold higher than the second threshold.

In order to maintain optimal functionality of the engine coolant system,the coolant level in the coolant reservoir may be maintained above athreshold level. The coolant may comprise a substantially 50-50 mixtureof water and glycol. As the coolant is circulated through enginecomponents to regulate engine temperature, over time, due toevaporation, the water content of the coolant may reduce and also theremay be an overall reduction in the coolant level and an increase in therelative glycol amount (to more than 50%) in the coolant. The coolantlevel in the coolant reservoir 15 may be estimated via the float sensor16. In response to a lower than threshold coolant level in the coolantreservoir, irrespective of the relative glycol amount in the coolant,water may be supplied from the water tank 63 to the coolant reservoir 15until the coolant level increases to the threshold level. Supplyingwater from the water tank to the coolant reservoir includes supplyingwater via a flow regulator valve 163 and a water line 161, an opening ofthe flow regulator valve 163 adjusted based on a demand for water supplyto the coolant reservoir, the opening increased with an increase in thedemand for water supply.

Chemical imbalance of the coolant and a higher level of glycol in thecoolant may result in engine system over heating and engine degradation.In one example, the relative glycol amount (such as glycol percentage)in the coolant may be directly measured via a dedicated glycol levelsensor 17. In another example, the glycol percentage may be estimatedfrom the coolant level in the reservoir. If it is inferred that thepercentage of glycol in the coolant is higher than the desired 50%(first higher threshold), an amount of water may be added to the coolantreservoir 15 such that the water glycol chemical balance is restored.The amount of water to be added may be based on the difference betweenthe actual relative glycol amount and the desired relative glycolamount. The water may then be added to the coolant reservoir 15 from thewater storage tank 63 via the water line 161 until the relative amountof glycol in the engine coolant decreases to the threshold amount. Anexample method for maintaining a water glycol balance in the coolantsystem is discussed with relation to FIG. 2. In one example, in responseto the relative amount of glycol in the engine coolant being lower thana lower second threshold amount, a diagnostic code may be set indicatingthe operator to externally supply glycol to the coolant reservoir toincrease the relative glycol amount in coolant to the threshold amount.

FIG. 1 further shows a control system 28. Control system 28 may becommunicatively coupled to various components of engine system 100 tocarry out the control routines and actions described herein. Controlsystem 28 may include an electronic digital controller 12. Controller 12may be a microcomputer, including a microprocessor unit, input/outputports, an electronic storage medium for executable programs andcalibration values, random access memory, keep alive memory, and a databus. Controller 12 may receive input from a plurality of sensors 30,such as the various sensors of FIG. 1, to receive input includingtransmission gear position, accelerator pedal position, brake demand,vehicle speed, engine speed, mass airflow through the engine, boostpressure, ambient conditions (temperature, pressure, humidity), etc.Other sensors include water storage level sensor 65, water temperaturesensor 67, conductivity sensor 93, coolant level sensor 16, glycol levelsensor 17, coolant temperature sensor 127, CAC 118 sensors, such as CACinlet air temperature, ACT sensor 125, exhaust pressure and temperaturesensors 80, 82, and pressure sensor 124, CAC outlet air temperaturesensor, and MCT sensor 23, knock sensor 183 for determining ignition ofend gases and/or water distribution among cylinders, and others. Thecontroller 12 receives signals from the various sensors of FIG. 1 andemploys the various actuators of FIG. 1 such as a flow regulator valve163, EGR valve 152, etc. to adjust engine operation based on thereceived signals and instructions stored on a memory of the controller.In one example, the controller may estimate a coolant level in thecoolant reservoir 15 via inputs from the coolant level (float) sensor 16and based on a lower than threshold coolant level, the controller maysend a signal to the actuator coupled to the flow regulation valve 163to allow water to be supplied to the coolant reservoir 15 from the waterstorage tank 63 until the coolant level increases to the thresholdcoolant level. In some examples, the storage medium may be programmedwith computer readable data representing instructions executable by theprocessor for performing the methods described below (e.g., at FIG. 2)as well as other variants that are anticipated but not specificallylisted.

In this way, the system of FIG. 1 provides for a vehicle systemcomprising: an engine, an engine coolant system including a coolantreservoir, an on-board water collection system including a water tank, awater lift pump, a regulator valve, and a water line coupling the watertank to the coolant reservoir, a float sensor and a glycol sensorcoupled to the coolant reservoir, a water quality sensor and a waterlevel sensor coupled to the water tank, an air conditioning systemincluding an evaporator and a first reservoir coupled to the water tankof the on-board water collection system, an exhaust gas recirculationsystem including a cooler and a second reservoir coupled to the watertank of the on-board water collection system, an engine intake systemincluding a charge air cooler and a third reservoir coupled to the watertank of the on-board water collection system, and a controller withcomputer readable instructions stored on non-transitory memory for:inferring a relative glycol amount in coolant based on inputs from theglycol sensor, and in response to a higher than first threshold relativeglycol amount, supplying water from the water tank to the coolantreservoir until the glycol percentage decreases to the thresholdpercentage, and in response to a lower than second lower thresholdrelative glycol amount, indicating a lower than threshold glycol amountby setting a diagnostic code.

FIG. 2 illustrates an example method 200 that may be implemented formaintaining a desired coolant level and a water glycol balance in anengine coolant system. Instructions for carrying out method 200 and therest of the methods included herein may be executed by a controllerbased on instructions stored on a memory of the controller and inconjunction with signals received from sensors of the engine system,such as the sensors described above with reference to FIG. 1. Thecontroller may employ engine actuators of the engine system to adjustengine operation, according to the methods described below.

At 202, the routine includes estimating and/or measuring engineoperating conditions. Conditions assessed may include, for example,driver demand, engine temperature, engine load, engine speed, exhausttemperature, ambient conditions including ambient temperature, pressure,and humidity, manifold pressure and temperature, boost pressure, exhaustair/fuel ratio, etc. Also, ambient conditions such as ambienttemperature, humidity, etc. may be measured.

At 204, a coolant level in a coolant reservoir (such as coolantreservoir 15 in FIG. 1) of the engine coolant system may be estimatedbased on inputs from a float sensor (such as float sensor 16 in FIG. 1)coupled to the coolant reservoir. Also, the controller may determine thecoolant level in the coolant reservoir based on input from a coolanttemperature sensor. If the coolant temperature is different from theexpected coolant temperature based on engine operating conditions, itmay be inferred that the coolant level is lower than the expectedcoolant level.

At 206, the routine includes determining if the coolant level in thecoolant reservoir is lower than a threshold level. The threshold levelmay correspond to the level of coolant required in the coolant system toreduce engine overheating and improve engine performance. As coolant iscirculated through heated engine components, water in the coolant mayevaporate, thereby causing a decrease in the total coolant level of thecoolant system. Further leaks in the coolant system may lead to loss incoolant and a lowering of the coolant level to below the thresholdlevel.

If it is determined that the coolant level in the coolant reservoir ishigher than or equal to the threshold level, it may be inferred that thecoolant in the coolant reservoir is at the desired level for optimalperformance of the coolant system. At 212, a relative glycol amount inthe coolant may be estimated via a distinct glycol level sensor coupledto the coolant reservoir. A coolant may originally comprise 50% waterand 50% glycol. As water is lost from the circulating coolant, theglycol content in the coolant may increase. Also, glycol may be lost dueto leakages in the coolant system.

In one example, during conditions when there is loss in coolant watercontent (such as due to evaporation), the amount of glycol in thecoolant may be estimated based on the coolant level by using equations1-4.

$\begin{matrix}{G_{old} = {\frac{y}{x_{old} + y} \times 100}} & (1) \\{G_{new} = {\frac{y}{x_{new} + y} \times 100}} & (2) \\{x_{new} = {x_{old} - C_{loss}}} & (3) \\{C_{loss} = {C_{old} - C_{new}}} & (4)\end{matrix}$

where, G_(old) is the original percentage of glycol in the coolant(before any loss in coolant water content), x_(old) is the originalamount of water in the coolant, y is the original amount of glycol inthe coolant, G_(new) is the current percentage of glycol in the coolant(after loss in coolant content), x_(new) is the current amount of waterin the coolant, C_(loss) is the amount of coolant lost during engineoperation, C_(old) is the original amount of coolant in the coolantreservoir, and C_(new) is the current amount of coolant in the coolantreservoir.

At 214, the routine includes determining if the relative glycol amountis higher than a threshold glycol amount. In one example, the relativeamount of glycol in the engine coolant is a percentage of glycol in theengine coolant as estimated via a glycol sensor coupled to the coolantreservoir, and the threshold amount of glycol is 50%. In anotherexample, the relative amount of glycol in the engine coolant is afraction of glycol in the engine coolant, and the threshold amount ofglycol is 0.5. If it is determined that the glycol level is not higherthan the threshold level, the routine proceeds to 218 to determine ifthe glycol level is lower than the threshold level. If it determinedthat the glycol level is not lower than the threshold level, it may beinferred that the relative glycol amount is substantially equal to thethreshold level and at 220, water supply to the coolant system forglycol level adjustment may be disabled.

However, if it is determined that the glycol level in coolant is lowerthan the threshold, it may be inferred that glycol needs to be added tothe coolant reservoir to maintain the water glycol balance in thecoolant system. At 222, a diagnostic code (such as flag) may be setindicating a lower than threshold glycol level in the coolant. Thediagnostic code may send a notification to the vehicle operator toexternally supply glycol to the coolant reservoir in order to improvecoolant system performance. Setting the diagnostic code is in responseto the relative amount of glycol in the engine coolant being lower thanthe threshold amount irrespective of the engine coolant level. As such,the diagnostic code may be set even when the coolant level is above thethreshold coolant level. In one example, the relative amount of glycolin the coolant may be compared to each of a first threshold and a secondthreshold, the first threshold higher than the second threshold, and ifthe glycol amount is in between the first threshold and the secondthreshold (lower than first threshold but higher than second threshold),the diagnostic flag may not be set as the reduced glycol level may notsubstantially affect the operation of the coolant system. However, ifthe relative glycol amount is lower than the second threshold, thediagnostic code may be set indicating requirement of external supply ofglycol. If it is determined at 214, that the glycol level in coolant ingreater than the threshold, at 216, the controller may determine theamount of water that may be added to the coolant to dilute the coolantand in turn reduce the relative glycol amount in the coolant to thethreshold amount. In one example, the amount of water to be injected tothe coolant reservoir may be estimated using equation 5.W ₁=2(G _(old) −G _(new))  (5)

Where W₁ is the amount of water to be injected to the coolant reservoirto restore the water glycol balance, G_(new) is the current amount ofglycol in the coolant and G_(old) is the threshold amount of glycol inthe coolant. As such, G_(old) may be 50% of the total amount of coolant.

In this way, a glycol content in coolant may be estimated via a glycolsensor coupled to the coolant reservoir, in response to a higher thanfirst threshold relative glycol amount in the coolant, water may besupplied from the water tank to the coolant reservoir until the relativeglycol amount in the coolant decreases to the threshold percentage whilenot notifying an operator, and in response to a lower than second lowerthreshold relative glycol amount in the coolant, an operator may benotified for external glycol supply, the first threshold relative glycolamount higher than the second threshold relative glycol amount.

If at 206, it is determined that the coolant level in the coolantreservoir is lower than the threshold coolant level, at 208, thecontroller may determine the amount of water that may be added to thecoolant to increase the coolant level in the reservoir to above thethreshold level and to restore the water-glycol balance in the coolant.In one example, the amount of water to be injected may be equal to theamount of coolant lost during engine operation, C_(loss).

Once the amount of water to be injected is determined for increasing thecoolant level to the threshold level and/or for attaining the thresholdglycol amount in the coolant (as determined in steps 208 and 216), theroutine moves to 210 to determine if the water level in a water tank orreservoir of an on-board water collection system is higher than a firstthreshold level, such as above 10% of capacity. If it is determined thatthe water level in the water tank is lower than the threshold, it may beinferred that there may not be sufficient water to be added to thecoolant reservoir for attaining a desirable coolant level and coolantwater glycol balance.

In response to the lower than first threshold water level in the tank,at 230, on-board collection of water from one or more vehicle systemssuch as condensate from one or more components, such as an EGR cooler, acharge air cooler, an AC evaporator, an exhaust heat exchanger, and avehicle external surface may be increased. The water tank may berefilled until the water level in the tank reaches a second thresholdlevel, the second threshold higher than the first threshold. Refillingthe water tank includes routing water from each of the one or morereservoirs to the water tank. As elaborated with reference to the systemof FIG. 1, the water reservoir may be refilled with, as non-limitingexamples, water condensed from exhaust passing through an EGR system,and water condensed from air passing through an evaporator of a vehicleair conditioning system. In one example, water from one or morereservoirs coupled to each of the water recovery system, (such as ACsystem, EGR system, exhaust system, etc.) may be routed to the watertank of the on-board water recovery system via operation of one or morepumps. The controller may send a signal to the actuators coupled to oneor more pumps of the on-board water recovery system to operate the pumpsin order to flow water collected in each of the reservoirs to the watertank. In one example, the controller may prioritize the water collectionfrom one or more engine systems based on engine operating conditions andthe amount of water available at the individual reservoir of eachsystem. In one example, if the AC system is operational, the controllermay first recover the condensate from the AC system and route it to thewater tank. In another example, if the AC system is not operating, andEGR is being supplied to the engine, the controller may first recoverwater condensed at the EGR cooler and supply it to the water tank. Inyet another example, during higher than threshold ambient humidity (suchas during rain), water may be first collected from the vehicle externalsurface and routed to the water tank. In a further example, thecontroller may estimate the amount of water stored in each of thereservoirs coupled to each of the water recovery systems, and may firstroute water to the water tank from the reservoir with the highest watercontent. In this way, on-board water collection may be increased andprioritized based on the amount of water desired and vehicle operatingconditions. Also, manual refill of the water tank may be requested.

As the water tank is being refilled, in response to a lower thanthreshold coolant content in the coolant reservoir, engine operatingparameters may be adjusted to reduce the possibility of overheatingcaused due to the lower level of coolant in the cooling system. In oneexample, if the engine temperature increases to above a thresholdtemperature, engine speed may be reduced to limit further rise in enginetemperature. Additionally, injections of fuel may be partially reducedin a “round-robin” fashion to further limit the rise in enginetemperature.

If it is determined that the water level in the water tank is higherthan the threshold level, at 224, the method includes estimating thequality of the water in the water reservoir. As such, the nature ofcontaminants present in the water, as well as the degree ofcontamination may vary widely based on the source of water used forrefilling the water tank. As an example, if water was obtained fromexternal vehicle surface (such as door seal channels in the door), theremay be a higher level of contaminants present. Also, it may berecommended to refill the water tank with distilled water, but theoperator may refill with tap water or well water instead. As such thedifferent sources of water may contain different types and amounts ofminerals and other contaminants that may cause deposits on waterfilters, water injectors, engine components, exhaust catalysts, etc. Inone example, the quality of the water in the water tank may be estimatedbased on the output of a water quality sensor coupled to the waterreservoir, the water quality estimate based on a conductivity value orionic strength of the water (such as sensed via a conductivity sensor).In alternate examples, the quality of the water may be estimated basedon an ionic strength of the water, a particle matter content, aturbidity sensor, a density sensor, a refraction index, etc.

In still other examples, the water quality may be inferred based on thewater refilling location using knowledge of the vehicle's location (suchas based on GPS data, location of nearby WiFi hotspots, etc.) combinedwith knowledge of the local water quality at that location (such asdetermined on-board or retrieved from a database, such as an internetdatabase of water quality for city water systems and ground water). Ifthe water quality value was inferred or retrieved from a remotelocation, the controller may additionally refine the data with previoushistory of contamination detected after refilling at the same location(as elaborated below). The history may be based on data collectedon-board the given vehicle, or collected on-board an alternate vehicleand retrieved through vehicle-to-vehicle (V2V) orvehicle-to-infrastructure communication. In one example, the quality ofthe water may be given an index value, or a rating number.

At 226, the estimated water quality (e.g., the index value or ratingnumber or conductivity value) is compared to a threshold which dependson the water quality sensor being used. For example, a lower reading ona turbidity sensor may be given a high water quality index value, andturbidity readings of less than 5 NTU may correspond to water qualityindex values higher than the threshold. The threshold may correspond toa minimum water quality level required to enable water supply to thecoolant reservoir without compromising engine cooling systemperformance.

If the estimated quality of the water is lower than the threshold, thenat 228, the method includes draining the water from the water reservoir,such as by opening a solenoid controlled drain valve coupling the waterreservoir to a drain pipe that releases the water to a location outsidethe vehicle. The water may be fully or partially drained, the selectionbased on the level of contamination of the water and/or based onpredictions of future water refills, water consumption rates, and watercondensate collection rates. In one example, if draining of the wateradded to the reservoir is selected, the controller may close the vehiclerefill tank cap or close a valve coupled in front of a tank inlet, whilediverting the incoming water to a drain.

In addition, if the water was refilled at a location off-board thevehicle, a memory of the controller may be updated, with GPS coordinateinformation of the location, to indicate that the source of the waterwas contaminated. Further, the controller may limit access to a refillport/cap of the water tank based on the indication of watercontamination. As a result, future water reservoir manual refills fromthat location may be limited, or at least temporarily disabled. In oneexample, an access door to the water tank refill port may be configuredwith a locking mechanism that is opened through a user interface, in avehicle cabin space, in communication with the controller. Thecontroller may issue location-based indications (e.g., warning beeps, orlights or messages displayed on a vehicle display on a center-console)when the local tap water or well water contamination level exceeds thethreshold level based on a predicted risk of contamination. Thecontroller may ask the vehicle operator to confirm that they arerefilling with the appropriate water (e.g., distilled water) by pressinga button or saying “yes” before allowing the water tank refill door toopen.

If the water quality is higher than the threshold, at 232, the estimatedamount of water may be supplied from the water tank of the on-boardwater collection system to the coolant reservoir of the coolant systemvia one or more water lines, a water lift pump, and a flow regulatorvalve in order to increase the coolant level to above the thresholdlevel and/or to decrease the relative glycol amount to the thresholdamount. The controller may send a signal to an actuator coupled to theflow regulator valve to adjust the opening of the flow regulator valvebased on the estimated amount of water to be supplied. In one example,the opening may be increased with an increase in the amount of water tobe supplied and the opening may be correspondingly decreased with adecrease in the amount of water to be supplied. Also, the controller maysend a signal to the actuator of the motor of the water lift pump toadjust the duration of operation of the pump based on the estimatedamount of water to be supplied. The controller may determine theduration of pump operation through a determination that directly takesinto account a determined amount of water to be injected, such asincreasing the duration of pump operation with increasing amount ofwater to be injected. The controller may alternatively determine theduration of pump operation based on a calculation using a look-up tablewith the input being the amount of water to be injected and the outputbeing the duration of pump operation. In this way, a quality of thewater in the water tank may be estimated based on a water qualitysensor; if the estimated quality is higher than a threshold, water maybe supplied to the coolant reservoir based on demand; and if theestimated quality is lower than a threshold, the water from the watertank may be drained.

Once water injection to the coolant reservoir is complete, at 234, theresultant relative glycol amount in the coolant may be measured based oninputs from the glycol level sensor. As such, water injection forincreasing the coolant level to above the threshold coolant level mayresult in over dilution of the coolant, resulting in a decrease in therelative glycol content in the coolant. Therefore, the routine mayproceed to 218 wherein it may again be determined if the new glycolamount is lower than the threshold amount. In response to a lower thanthreshold relative glycol amount in the coolant, the operator may benotified by setting a diagnostic code that external supply of glycol isrequested to improve the performance of the engine coolant system. Inthis way, after supplying water to the coolant reservoir, the relativeglycol amount in the engine coolant may be estimated, and in response toa lower than threshold glycol amount, a diagnostic code may be set.

In this way, in response to a lower than threshold coolant level in acoolant reservoir, water may be supplied from a water tank of anon-board water collection system to the coolant reservoir until acoolant level in the coolant reservoir increases to the threshold level,and in response to a lower than first threshold water level in the watertank, water from one or more water reservoirs coupled to one or morevehicle systems may be supplied to the water tank until a water level inthe water tank increases to above a second threshold water level, thesecond threshold higher than the first threshold.

FIG. 3 shows an example operating sequence 300 illustrating maintenanceof a coolant level and a relative glycol amount in an engine coolantusing water from an on-board water recovery system. The horizontal(x-axis) denotes time and the vertical markers t1-t5 identifysignificant times in the maintenance schedule of the coolant system.

The first plot, line 302, shows a variation in coolant temperature overtime, as inferred based on inputs from an engine coolant temperaturesensor. The second plot, line 304, shows a variation in coolant level inthe coolant reservoir over time, as inferred based on inputs from acoolant level sensor. Dotted line 305 represents a threshold coolantlevel below which water is requested to be added to the coolantreservoir to improve functionality of the engine coolant system. Thethird plot, line 306, shows a change in a relative glycol amount in thecoolant, as inferred based on inputs from a glycol level sensor. Dottedline 307 represents a threshold glycol amount in the engine coolant thatis desired to be maintained for optimal operation of the coolant system.The fourth plot, line 308, shows a level of water in the water tank ofthe on-board water recovery system, as inferred based on inputs from awater level sensor. Dotted line 309 represents a first threshold waterlevel, below which water may not be supplied to the coolant reservoir.Dotted line 311 represents a second threshold water level, above whichwater supply to the coolant reservoir may be suspended. The fifth plot,line 310, shows a level of water injected (supplied) from the water tankof the on-board water recovery system to the coolant reservoir. Thefifth plot, line 312, shows a position of a diagnostic flag indicatingrequirement for external addition of glycol to the coolant reservoir.

Prior to time t1, the coolant temperature gradually increases causingwater present in the coolant to evaporate. Consequently, it is observedthat water evaporation causes the coolant level to reduce. As waterevaporates, the relative glycol amount or percentage in the coolant mayincrease to above the threshold amount. For optimal performance of thecoolant system, the relative glycol amount in the coolant may bemaintained at 50%. During this time, the coolant level 304 in thecoolant reservoir is above the threshold 305 and water injection fromthe water tank to the coolant reservoir is not carried out. Since thecoolant level is above the threshold level, the diagnostic flag ismaintained in the off position (no indication to operator).

At time t1, it is observed that the coolant level 304 in the coolanttank has decreased to below the threshold 305 and relative glycol amount306 in coolant has increased to above the threshold 307. In response tothe decrease in the coolant level and the increase in the relativeglycol amount, between time t1 and t2, water from the water tank issupplied to the coolant tank via a water line, a water lift pump, and aflow regulator valve. As the water is routed from the water tank, thewater level in the water tank decreases while the coolant level in thecoolant tank increases. Also, the dilution (water content) of thecoolant increases, the relative glycol amount in the coolant decreases.

At time t2, it is observed that the coolant level in the coolantreservoir has increased to above the threshold 305 and also, therelative glycol amount in coolant has decreased to the threshold amount307. In response to the increase in coolant level and the decrease inthe relative glycol amount, further water supply from the water tank tothe coolant reservoir is suspended. Between time t2 and t3, the coolantlevel continues to remain above the threshold level 305 and the relativeglycol amount remains at the threshold amount 307. The water in thewater tank is used in other system systems such as for water injectionto the engine and the water level in the tank decreases.

At time t3, it is observed that the coolant level in the coolant tankhas decreased to below the threshold 305 and relative glycol amount incoolant has increased above the threshold 307. However, at this time,the water level in the water tank is below the threshold 309 and waterfrom the tank cannot be supplied to the coolant tank for increasing thecoolant level. Between time t3 and t4, water collection from one or morevehicle systems is increased to refill the tank and increase the waterlevel in the tank to above the threshold. In response to the lower thanthreshold water level in the water tank, on-board water collection isincreased by one or more of collecting condensate from the evaporator ofthe air conditioning system in a first reservoir, collecting condensatefrom the cooler of the exhaust gas recirculation system in a secondreservoir, and collecting condensate from the charge air cooler of theengine intake system in a third reservoir, and then supplying watercollected in each of the first reservoir, the second reservoir, and thethird reservoir to the water tank. As the on-board water recoveryincreases from a plurality of vehicle systems, the water level in thewater tank gradually increases.

At time t4, it is observed that the water level in the water tank hasincreased to above the second threshold 311 and water supply to thecoolant reservoir is initiated. Relative to the demand for water at timet1, the demand for water at this time t4 is higher due to a graterreduction in coolant level. Therefore, the amount of water injectedbetween time t4 and t5 is higher than the amount of water injectedbetween time t1 and t2.

At time t5, it is observed that the coolant level has increased to abovethreshold 305. However, it is inferred that due to the addition ofwater, the relative glycol amount in the coolant decreases tosignificantly below the threshold 307 by more than a threshold amount(not shown) and glycol needs to be externally added to the coolant tankto restore the water glycol chemical balance. Therefore, at time t5, adiagnostic flag (code) may be turned on to notify the operator regardingthe requirement of external glycol supply.

In this way, a water level and a relative glycol amount may bemaintained in an engine coolant by using water sourced from one or moreon-board vehicle systems.

One example method comprises, in response to a relative amount of glycolin an engine coolant being higher than a threshold amount, and/or inresponse to an engine coolant level being lower than a threshold coolantlevel, supplying water from an on-board water collection system to acoolant reservoir; and in response to the relative amount of glycol inthe engine coolant being lower than the threshold amount, setting adiagnostic code. In the preceding example, additionally or optionally,supplying water from the on-board water collection system includessupplying water from a water tank of the on-board water collectionsystem to the engine coolant reservoir until the engine coolant levelincreases to the threshold coolant level, and wherein setting thediagnostic code is in response to the relative amount of glycol in theengine coolant being lower than the threshold amount irrespective of theengine coolant level. Any or all of the preceding examples furthercomprising, additionally or optionally, after supplying water to thecoolant reservoir, estimating the relative glycol amount in the enginecoolant, and in response to a lower than threshold glycol amount,setting the diagnostic code. In any or all of the preceding examples,additionally or optionally, supplying water from the on-board watercollection system to the coolant reservoir further includes supplyingwater to the engine coolant reservoir until the relative amount ofglycol in the engine coolant decreases to the threshold amount. In anyor all of the preceding examples, additionally or optionally, therelative amount of glycol in the engine coolant is a percentage ofglycol in the engine coolant as estimated via a glycol sensor coupled tothe coolant reservoir, and wherein the threshold amount of glycol is50%. In any or all of the preceding examples, additionally oroptionally, the on-board water collection system sources water from oneor more vehicle system including an on-board air-conditioning system, anexhaust gas recirculation system, an exhaust system, and an air intakesystem. In any or all of the preceding examples, additionally oroptionally, each of the one or more vehicle systems include one or morereservoirs and refilling the water tank includes routing water from eachof the one or more reservoirs to the water tank. Any or all of thepreceding examples further comprising, additionally or optionally,collecting condensate from an evaporator of the on-board airconditioning system in a first water reservoir, and then routing waterfrom the first water reservoir to the water tank via water lines. Any orall of the preceding examples further comprising, additionally oroptionally, collecting rain water and atmospheric condensate from anexternal vehicle surface, and routing the water to the water tank,wherein the external vehicle surface includes door seal channels. Any orall of the preceding examples further comprising, additionally oroptionally, estimating a quality of the water in the water tank based ona water quality sensor; if the estimated quality is higher than athreshold, supplying the water to the coolant reservoir based on demand;and if the estimated quality is lower than a threshold, draining thewater from the water tank. Any or all of the preceding examples furthercomprising, additionally or optionally, if a water level in the watertank is higher than a first threshold or if a predicted watertemperature is lower than a freezing temperature, draining at least aportion of water from the water tank, and if the water level in thewater tank is lower than a second threshold, refilling the water tankwith water collected from the one or more vehicle systems, the firstthreshold higher than the second threshold.

Another example engine method comprises: in response to a lower thanthreshold coolant level in a coolant reservoir, supplying water from awater tank of an on-board water collection system to the coolantreservoir until a coolant level in the coolant reservoir increases tothe threshold level, and in response to a lower than first thresholdwater level in the water tank, supplying water from one or more waterreservoirs coupled to one or more vehicle systems to the water tankuntil a water level in the water tank increases to above a secondthreshold water level, the second threshold higher than the firstthreshold. The preceding example further comprising, additionally oroptionally, estimating a glycol content in coolant via a glycol sensorcoupled to the coolant reservoir, in response to a higher than firstthreshold relative glycol amount in the coolant, supplying water fromthe water tank to the coolant reservoir until the relative glycol amountin the coolant decreases to the threshold percentage while not notifyingan operator, and in response to a lower than second lower thresholdrelative glycol amount in the coolant, notifying an operator forexternal glycol supply, the first threshold relative glycol amounthigher than the second threshold relative glycol amount.

In any or all of the preceding examples, additionally or optionally,supplying water from the water tank to the coolant reservoir includessupplying water via a flow regulator valve and a water line, an openingof the flow regulator valve adjusted based on a demand for water supplyto the coolant reservoir, the opening increased with an increase in thedemand for water supply. In any or all of the preceding examples,additionally or optionally, supplying water from the water tank to thecoolant reservoir further includes, estimating a water quality in thewater tank via a conductivity sensor, in response to a higher thanthreshold water quality, opening the flow regulator valve to supplywater to the coolant reservoir, and in response to a lower thanthreshold water quality, opening a drain valve to drain water from thewater tank. In any or all of the preceding examples, additionally oroptionally, the one or more vehicle systems include an engine intakesystem comprising a charge air cooler, condensate from the charge aircooler is collected in one of the one or more water reservoirs andsupplied to the water tank in response to the water level in the watertank reducing to below the first threshold. In any or all of thepreceding examples, additionally or optionally, the one or more vehiclesystems further include an exhaust gas recirculation system comprisingan exhaust gas recirculation cooler, condensate from the exhaust gasrecirculation cooler is collected in one of the one or more waterreservoirs and supplied to the water tank in response to the water levelin the water tank reducing to below the first threshold.

In yet another example, a vehicle system comprises an engine; an enginecoolant system including a coolant reservoir; an on-board watercollection system including a water tank, a water lift pump, a regulatorvalve, and a water line coupling the water tank to the coolantreservoir; a float sensor and a glycol sensor coupled to the coolantreservoir; a water quality sensor and a water level sensor coupled tothe water tank; an air conditioning system including an evaporator and afirst reservoir coupled to the water tank of the on-board watercollection system; an exhaust gas recirculation system including acooler and a second reservoir coupled to the water tank of the on-boardwater collection system; an engine intake system including a charge aircooler and a third reservoir coupled to the water tank of the on-boardwater collection system; and a controller with computer readableinstructions stored on non-transitory memory for: inferring a relativeglycol amount in coolant based on inputs from the glycol sensor; and inresponse to a higher than first threshold relative glycol amount,supplying water from the water tank to the coolant reservoir until theglycol percentage decreases to the threshold percentage, and in responseto a lower than second lower threshold relative glycol amount,indicating a lower than threshold glycol amount by setting a diagnosticcode. In the preceding example, additionally or optionally, controllerincludes further instructions for: in response to a lower than thresholdwater level in the water tank, increasing on-board water collection byone or more of collecting condensate from the evaporator of the airconditioning system in the first reservoir, collecting condensate fromthe cooler of the exhaust gas recirculation system in the secondreservoir, and collecting condensate from the charge air cooler of theengine intake system in the third reservoir, and then supplying watercollected in each of the first reservoir, the second reservoir, and thethird reservoir to the water tank. In any or all of the precedingexamples, additionally or optionally, the controller includes furtherinstructions for: in response to a lower than threshold coolant level inthe coolant reservoir, irrespective of the relative glycol amount in thecoolant, supplying water from the water tank to the coolant reservoiruntil the coolant level increases to the threshold level.

In this way, by continuously monitoring a coolant level in the coolantreservoir of an engine coolant system and opportunistically adding waterto the coolant, a desired coolant level may be maintained, therebyreducing a possibility of engine overheating. By supplying water to thecoolant responsive to the relative glycol amount in coolant increasingto above a threshold, the water glycol balance in the coolant may bemaintained. The technical effect of sourcing water from a plurality ofon-board vehicle components such as the air conditioning system for usein the coolant system is that manual refill of water is not required,thereby reducing maintenance costs. Also, by assessing the water qualitybefore adding the water to the coolant system, possibility ofcontamination of the coolant system may be reduced.

Note that the example control and estimation routines included hereincan be used with various engine and/or vehicle system configurations.The control methods and routines disclosed herein may be stored asexecutable instructions in non-transitory memory and may be carried outby the control system including the controller in combination with thevarious sensors, actuators, and other engine hardware. The specificroutines described herein may represent one or more of any number ofprocessing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various actions,operations, and/or functions illustrated may be performed in thesequence illustrated, in parallel, or in some cases omitted. Likewise,the order of processing is not necessarily required to achieve thefeatures and advantages of the example embodiments described herein, butis provided for ease of illustration and description. One or more of theillustrated actions, operations and/or functions may be repeatedlyperformed depending on the particular strategy being used. Further, thedescribed actions, operations and/or functions may graphically representcode to be programmed into non-transitory memory of the computerreadable storage medium in the engine control system, where thedescribed actions are carried out by executing the instructions in asystem including the various engine hardware components in combinationwith the electronic controller.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above technology can be applied to V-6,I-4, I-6, V-12, opposed 4, and other engine types. The subject matter ofthe present disclosure includes all novel and non-obvious combinationsand sub-combinations of the various systems and configurations, andother features, functions, and/or properties disclosed herein.

The following claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

The invention claimed is:
 1. An engine method, comprising: in responseto a relative amount of glycol in an engine coolant being higher than athreshold amount, and in response to an engine coolant level being lowerthan a threshold coolant level during increase coolant temperaturelevels, selectively supplying water from an on-board water collectionsystem to a coolant reservoir based on water quality.
 2. The method ofclaim 1, wherein supplying water from the on-board water collectionsystem includes supplying water from a water tank of the on-board watercollection system to the engine coolant reservoir until the enginecoolant level increases to the threshold coolant level.
 3. The method ofclaim 1, further comprising, adjusting an amount of water injectionresponsive to coolant level.
 4. The method of claim 1, wherein supplyingwater from the on-board water collection system to the coolant reservoirfurther includes supplying water to the engine coolant reservoir untilthe relative amount of glycol in the engine coolant decreases to thethreshold amount.
 5. The method of claim 1, wherein the on-board watercollection system sources water from an on-board air-conditioningsystem.
 6. The method of claim 1, wherein the on-board water collectionsystem sources water from an exhaust gas system.
 7. The method of claim1, wherein the on-board water collection system sources water from anexhaust system, and wherein the collection system includes one or morereservoirs, and refilling the water tank includes routing water fromeach of the one or more reservoirs to the water tank.
 8. The method ofclaim 5, further comprising, collecting condensate from an evaporator ofthe on-board air conditioning system in a first water reservoir, andthen routing water from the first water reservoir to the water tank viawater lines.
 9. The method of claim 1, further comprising, collectingrain water and atmospheric condensate from an external vehicle surface,and routing the water to the water tank, wherein the external vehiclesurface includes door seal channels.
 10. The method of claim 1, furthercomprising, estimating the quality of the water in the water tank basedon a water quality sensor; if the estimated quality is higher than athreshold, supplying the water to the coolant reservoir based on demand;and if the estimated quality is lower than a threshold, draining thewater from the water tank.
 11. The method of claim 1, furthercomprising, if a water level in the water tank is higher than a firstthreshold or if a predicted water temperature is lower than a freezingtemperature, draining at least a portion of water from the water tank,and if the water level in the water tank is lower than a secondthreshold, refilling the water tank with water collected from the one ormore vehicle systems, the first threshold higher than the secondthreshold.
 12. An engine method, comprising: in response to a lower thanthreshold coolant level in a coolant reservoir, supplying water from awater tank of an on-board water collection system to the coolantreservoir until a coolant level in the coolant reservoir increases tothe threshold level, and in response to a lower than first thresholdwater level in the water tank, selectively supplying water from one ormore water reservoirs coupled to one or more vehicle systems to thewater tank until a water level in the water tank increases to above asecond threshold water level, the second threshold higher than the firstthreshold responsive to a water quality.
 13. The method of claim 12,further comprising, estimating a glycol content in coolant via a glycolsensor coupled to the coolant reservoir, in response to a higher thanfirst threshold relative glycol amount in the coolant, supplying waterfrom the water tank to the coolant reservoir until the relative glycolamount in the coolant decreases to the threshold percentage while notnotifying an operator, and in response to a lower than second lowerthreshold relative glycol amount in the coolant, notifying an operatorfor external glycol supply, the first threshold relative glycol amounthigher than the second threshold relative glycol amount.
 14. The methodof claim 12, wherein supplying water from the water tank to the coolantreservoir includes supplying water via a flow regulator valve and awater line, an opening of the flow regulator valve adjusted based on ademand for water supply to the coolant reservoir, the opening increasedwith an increase in the demand for water supply.
 15. The method of claim14, wherein supplying water from the water tank to the coolant reservoirfurther includes, estimating the water quality in the water tank via aconductivity sensor, in response to a higher than threshold waterquality, opening the flow regulator valve to supply water to the coolantreservoir, and in response to a lower than threshold water quality,opening a drain valve to drain water from the water tank.
 16. The methodof claim 12, wherein the one or more vehicle systems include an engineintake system comprising a charge air cooler, condensate from the chargeair cooler is collected in one of the one or more water reservoirs andsupplied to the water tank in response to the water level in the watertank reducing to below the first threshold.
 17. The method of claim 12,wherein the one or more vehicle systems further include an exhaust gasrecirculation system comprising an exhaust gas recirculation cooler,condensate from the exhaust gas recirculation cooler is collected in oneof the one or more water reservoirs and supplied to the water tank inresponse to the water level in the water tank reducing to below thefirst threshold.
 18. A vehicle system, comprising: an engine; an enginecoolant system including a coolant reservoir; an on-board watercollection system including a water tank, a water lift pump, a regulatorvalve, and a water line coupling the water tank to the coolantreservoir; a float sensor and a glycol sensor coupled to the coolantreservoir; a water quality sensor and a water level sensor coupled tothe water tank; an air conditioning system including an evaporator and afirst reservoir coupled to the water tank of the on-board watercollection system; an exhaust gas recirculation system including acooler and a second reservoir coupled to the water tank of the on-boardwater collection system; an engine intake system including a charge aircooler and a third reservoir coupled to the water tank of the on-boardwater collection system; and a controller with computer readableinstructions stored on non-transitory memory for: inferring a relativeglycol amount in coolant based on inputs from the glycol sensor; inresponse to a higher than first threshold relative glycol amount,supplying water from the water tank to the coolant reservoir until theglycol percentage decreases to the threshold percentage, and in responseto a lower than second lower threshold relative glycol amount,indicating a lower than threshold glycol amount by setting a diagnosticcode; and routing collected water to the water tank based on quality ofthe collected water.
 19. The system of claim 18, wherein the controllerincludes further instructions for: in response to a lower than thresholdwater level in the water tank, increasing on-board water collection byone or more of collecting condensate from the evaporator of the airconditioning system in the first reservoir, collecting condensate fromthe cooler of the exhaust gas recirculation system in the secondreservoir, and collecting condensate from the charge air cooler of theengine intake system in the third reservoir, and then supplying watercollected in each of the first reservoir, the second reservoir, and thethird reservoir to the water tank.
 20. The system of claim 18, whereinthe controller includes further instructions for: in response to a lowerthan threshold coolant level in the coolant reservoir, irrespective ofthe relative glycol amount in the coolant, supplying water from thewater tank to the coolant reservoir until the coolant level increases tothe threshold level.